1. Technical Field
The present invention relates to a developing unit.
2. Related Art
In the trickle method, a developer, in which toner and carrier are mixed-together in advance, is housed in a developer cartridge, and, simultaneously with the supplying of the toner from the developer cartridge to a developing unit, new carrier also is supplied bit-by-bit. Because the amount of the developer within the developing unit increases at this time, when an amount which is greater than or equal to a given amount has accumulated, the excess developer is discharged to the exterior of the developing unit. Accordingly, the developer is stable and does not deteriorate, i.e., the charge amount thereof does not fall to less than or equal to a predetermined value.